A type of machine for providing cyclic or non-cyclic stresses to a material presently exists of a nature such that very expensive servo controlled hydraulics are employed to control force, stroke, and cycle rate. While these machines are capable of operating over a wide range of speeds, the disadvantages are high initial cost for both hardware and software, as well as high filtration requirements of the hydraulic system to prevent contamination and damage to any of the sophisticated hydraulic components. Maintenance of these machines are costly and is usually performed by a specialist in hydraulics and other specialists for solving computer hardware and software problems.
Another type of machine in use in this field is electrically controlled sliding members, often driven by a rotating screw. While this is lower in cost than the first example, it is not nearly as capable of high cyclic rates and loads.
Machines for providing stresses to material have also been described in the patent literature. For example U.S. Pat. No. 5,421,205 "Apparatus for the rapid ultimate material strength testing" of A. Pohl, U.S. Pat. No. 3,733,895 high speed fatigue tester by Ishida, and U.S. Pat. No. 3,808,885, a Spring tester by Carlson, incorporated herein by reference, are presented for the background of the reader.
These and other approaches do not offer the same advantages as the present invention. In particular there is a need for cost effective devices, devices which are simple to operate, which are minimal upkeep and which can be easily adapted to a variety of test conditions and part configurations.